Shock wave guide wire

ABSTRACT

A guide wire, for use, for example, in guiding an elongated catheter through an artery or vein of a mammalian body having a stenosis and/or an occlusion therein, includes an elongated conductor having a longitudinal dimension, a proximal end and a distal end. The guide wire further includes an insulator overlying the elongated conductor. The insulator exposes a portion of the longitudinal dimension of the elongated conductor to form an electrode. The elongated conductor is arranged to be connected to a source of high voltage pulses to cause electrical arcs at the electrode that in turn form steam bubbles and shock waves to break the stenosis and/or open the occlusion and permit the guide wire to pass there through. Other embodiments are directed to a system including the guide wire and a method of using the guide wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/273,063, filed May 8, 2014 of which is hereby incorporated byreference in its entirety.

BACKGROUND

The present invention relates to a treatment and system for crossing anarterial lesion in order to dilate the lesion and restore normal bloodflow in the artery. Such devices and methods may be used as part of aballoon angioplasty procedure. Calcified lesions require high pressures(sometimes as high as 10-15 or even 30 atmospheres) to break thecalcified plaque and push it back into the vessel wall. With suchpressures comes trauma to the vessel wall which can contribute to vesselrebound, dissection, thrombus formation, and a high level of restenosis.Non-concentric calcified lesions can result in undue stress to the freewall of the vessel when exposed to high pressures.

Angioplasty balloons have been employed to treat such lesions. Wheninflated to high pressures, angioplasty balloons can have a specificmaximum diameter to which they will expand. Generally, the opening inthe vessel under a concentric lesion will typically be much smaller. Asthe pressure is increased to open the passage way for blood flow, theballoon will be confined to the size of the opening in the calcifiedlesion (before it is broken open). As the pressure builds, a tremendousamount of energy is stored in the balloon until the calcified lesionbreaks or cracks. That energy is then released and results in the rapidexpansion of the balloon to its maximum dimension and may stress andinjure the vessel walls.

Recently, a new system and method has been contemplated for breaking upcalcium deposits in, for example, arteries and veins. Such a system isdescribed, for example in U.S. Patent Publication No. 2009/0312768,Published Dec. 17, 2009. Embodiments described therein include acatheter having balloon, such as an angioplasty balloon, at the distalend thereof arranged to be inflated with a fluid. Disposed within theballoon is a shock wave generator that may take the form of, forexample, a pair of electrodes, which are coupled to a high voltagesource at the proximal end of the catheter through a connector. When theballoon is placed adjacent a calcified region of a vein or artery and ahigh voltage pulse is applied across the electrodes, a shock wave isformed that propagates through the fluid and impinges upon the wall ofthe balloon and the calcified region. Repeated pulses break up thecalcium without damaging surrounding soft tissue.

Arteries are sometimes totally occluded with a thrombus, plaque, fibrousplaque, and/or calcium deposits. When this condition is present, thephysician must first pass a soft narrow guide wire down the artery andthrough the occluded area. The guide wire may be as small as 0.014inches in diameter and usually has a soft flexible tip to help avoidpenetrating the artery wall in artery corners. The angioplasty balloonis then fed down the artery on the guide wire to the desired location ofthe blockage. Unfortunately, many times the physician is faced with achronic occlusion which is not passable with a guide wire. This occurswhen the occlusion is so tight and solid that the soft guide wire cannotpenetrate through it. Stiffer guide wires may be used in these cases,but they must be used very carefully because they can easily penetratethe artery wall when forced against the chronic total occlusion.

Guide wires have been proposed that utilize radio frequency energy toopen the occlusion. Unfortunately, the heat generated by the radiofrequency energy to open the occlusion is intense and can damage thewalls of the artery or vessel. The radio frequency energy produces aplasma which burns anything in its path. Hence, such systems must beused carefully and must be continuously moved without pause to avoidartery or vessel damage. Moreover, such an approach requires a centeringmechanism that keeps the plasma centered in the artery or vessel. Suchcentering is difficult to achieve, especially in the corners and bendsof the arteries or veins.

Hence, there is a need for an apparatus and procedure for opening atotal occlusion enough to permit a guide wire and angioplasty balloon tobe fed there through. Most desirably, such an apparatus and procedurewould avoid damage the artery or vessel and further be compatible withthe use of the aforementioned shock wave catheter systems describedabove. The present invention addressed these and other issues.

SUMMARY

In one embodiment, a guide wire for use in, for example, guiding anelongated catheter through an artery or vein of a mammalian body havinga stenosis and/or an occlusion therein, includes an elongated conductorhaving a longitudinal dimension, a proximal end and a distal end. Theguide wire further includes an insulator overlying the elongatedconductor. The insulator exposes a portion of the longitudinal dimensionof the elongated conductor to form an electrode. The elongated conductoris arranged to be connected to a source of high voltage pulses to causeelectrical arcs at the electrode that in turn form steam bubbles andshock waves to break the stenosis and/or open the occlusion and permitthe guide wire to pass there through.

The elongated conductor may have a distal tip end at the distal end ofthe elongated conductor and the electrode may be at the distal tip endof the elongated conductor. The distal tip end of the elongatedconductor may be generally spherical in configuration. The distal tipend may be formed of stainless steel.

The insulator may be formed of Teflon. The elongated conductor andinsulator may form a flexible coiled structure at the distal end of theelongated conductor. The distal tip end of the elongated conductor maybe generally spherical in configuration.

The guide wire may further include an anchor. The anchor may bereleasable to permit the elongated conductor and insulator to be movedlongitudinally and rotated.

In another embodiment, a guide wire system, for use, for example, inguiding an elongated catheter through an artery or vein of a mammalianbody having a stenosis and/or an occlusion therein includes a guide wireincluding an elongated conductor having a longitudinal dimension, aproximal end and a distal end and an insulator overlying the elongatedconductor. The insulator exposes a portion of the longitudinal dimensionof the elongated conductor to form an electrode. The system furtherincludes a source of high voltage pulses to cause electrical arcs at theelectrode that in turn form steam bubbles and shock waves to break thestenosis and/or open the occlusion.

The source of high voltage may be arranged to provide the elongatedconductor with a high electrical voltage at a comparatively low initialcurrent through the elongated conductor and terminate the highelectrical voltage in response to a comparatively high current throughthe elongated conductor.

The source of high voltage may be arranged to deliver a first electricalvoltage to the electrode that grows a bubble at the electrode and thenthereafter to deliver a second electrical voltage to the electrode tocreate an arc at the electrode and to rapidly expand the bubble to forma shock wave.

The elongated conductor of the guide wire has a distal tip end at thedistal end of the elongated conductor and wherein the electrode may beat the distal tip end of the elongated conductor. The distal tip end ofthe elongated conductor may be generally spherical in configuration. Thedistal tip end may be formed of stainless steel. The insulator may beformed of Teflon.

The elongated conductor and insulator of the guide wire may beconfigured to form a flexible coiled structure at the distal end of theelongated conductor. The distal tip end of the elongated conductor maybe generally spherical in configuration.

The system may further include an anchor, the anchor being releasable topermit the elongated conductor and insulator to be moved longitudinallyand rotated.

In a still further embodiment, a method for use, for example, in guidingan elongated catheter through an artery or vein of a mammalian bodyhaving a stenosis and/or an occlusion therein includes the steps ofproviding an elongated conductor having a longitudinal dimension, aproximal end, a distal end and an insulator overlying the elongatedconductor. The insulator exposes a portion of the longitudinal dimensionof the elongated conductor to form an electrode. The method furtherincludes the steps of inserting the elongated conductor into an arteryor vein until a stenosis and/or an occlusion is reached and applying atleast one high voltage pulse to the elongated conductor to cause atleast one electrical arc at the electrode that in turn forms at leastone steam bubble and shock wave to break the stenosis and/or open theocclusion.

The step of applying the at least one high voltage pulse to theelongated conductor may include providing the elongated conductor with ahigh electrical voltage at a comparatively low initial current throughthe elongated conductor and terminating the high electrical voltage inresponse to a comparatively high current through the elongatedconductor.

The step of applying the at least one high voltage pulse to theelongated conductor may include delivering a first electrical voltage tothe electrode that grows a bubble at the electrode and then thereafterdelivering a second electrical voltage to the electrode to create an arcat the electrode and to rapidly expand the bubble to form a shock wave.

One variation of a method for opening a vascular occlusion describedherein may comprise advancing a shock wave guide wire within thevasculature to contact the vascular occlusion, where the shock waveguide wire comprises an elongated conductor with a conductive distal tipand an insulator overlying the elongate conductor without covering theconductive distal tip, advancing an angioplasty balloon catheter overthe shock wave guide wire to the vascular occlusion, generating one ormore shock waves using the guide wire to create one or more openings inthe occlusion, and advancing the angioplasty balloon catheter into theone or more openings to perform an angioplasty procedure. In somevariations, the method may also include attaching a return electrode orpad to a patient's skin. The method may also comprise visualizing thevascular occlusion, for example, by injecting a dye from the angioplastyballoon catheter, and/or confirming the location of the shock wave guidewire and/or the angioplasty balloon catheter prior to generating one ormore shock waves. In some variations, the method may further comprisingcentering the distal tip of the shock wave guide wire within thevascular lumen prior to generating one or more shock waves, wherecentering the distal tip of the shock wave guide wire may compriseexpanding the angioplasty balloon of the angioplasty balloon catheter.Advancing the angioplasty balloon catheter into the one or more openingsto perform an angioplasty procedure may comprise inflating the balloonto further open the occlusion. The angioplasty balloon catheter maycomprise one or more shock wave electrodes within the balloon andadvancing the angioplasty balloon catheter into the one or more openingsto perform an angioplasty procedure may comprise generating one or moreshock waves within the angioplasty balloon to further open theocclusion.

Another variation of a method for opening a vascular occlusion maycomprise advancing a shock wave guide wire within the vasculature tocontact the vascular occlusion, where the shock wave guide wirecomprises an elongated conductor with a conductive distal tip and aninsulator overlying the elongate conductor without covering theconductive distal tip, and generating one or more shock waves using theguide wire to create one or more openings in the occlusion. In somevariations, the method may also include attaching a return electrode orpad to a patient's skin. The method may optionally comprise visualizingthe vascular occlusion prior to generating one or more shock waves. Insome variations, the method may further comprise advancing anangioplasty balloon catheter over the shock wave guide wire to the oneor more openings in the vascular occlusion to perform an angioplastyprocedure. The angioplasty balloon catheter may comprise one or moreshock wave electrodes within the balloon, and advancing the angioplastyballoon catheter into the one or more openings to perform an angioplastyprocedure may comprise generating one or more shock waves within theangioplasty balloon to further open the occlusion. Optionally, themethod may further comprise centering the distal tip of the shock waveguide wire within the vascular lumen prior to generating one or moreshock waves. Centering the distal tip of the shock wave guide wire maycomprise expanding the angioplasty balloon of the angioplasty ballooncatheter.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The variousdescribed embodiments of the invention, together with representativefeatures and advantages thereof, may best be understood by makingreference to the following description taken in conjunction with theaccompanying drawings, in the several figures of which like referencenumerals identify identical elements, and wherein:

FIG. 1 is a perspective view, with portions cut away, of a shock waveguide wire system embodying aspects of the invention;

FIG. 2 is a perspective view, with portions cut away, showing furtherdetails of the shock wave guide wire system of FIG. 1 in use with anangioplasty catheter;

FIG. 3 is a perspective view, with portions cut away, showing stillfurther details of the shock wave guide wire system of FIG. 1 in usewith an angioplasty catheter;

FIG. 4 is a perspective view of the guide wire of the shock wave guidewire system of FIG. 1 illustrating further aspects of the invention;

FIG. 5 is a perspective view to an enlarged scale of the distal end ofthe shock wave guide wire illustrating further aspects of the invention;

FIG. 6 is a perspective view, to an exploded scale, illustratingparticular aspects of the distal tip electrode of the shock wave guidewire of FIG. 4;

FIG. 7 is a graph illustrating a manner in which a shock wave guide wiresystem embodying the invention may be operated according to anembodiment of the invention;

FIG. 8 is a schematic diagram of a power source for use in a shock waveguide wire system according to an embodiment of the invention;

FIG. 9 is a schematic diagram of a power source for use in an a shockwave guide wire system according to another embodiment of the invention;and

FIG. 10 is a graph illustrating another manner in which a shock waveguide wire system embodying the invention may be operated according toan embodiment of the invention with the power circuit of FIG. 9.

FIG. 11A is a flow diagram that depicts one variation of method thatuses a shock wave guide wire system. FIG. 11B is a flow diagram thatdepicts another variation of a method that uses a shock wave guide wiresystem.

DETAILED DESCRIPTION

FIG. 1 is a partial cut away view of a blood vessel 50 (e.g., an arteryor vein) of a heart (or other body part) being treated with a shock waveguide wire system 20 embodying aspects of the invention. The bloodvessel has a stenosis or chronic total occlusion 52 being opened by thesystem 20. The system 20 generally includes a guide wire 22 embodyingthe invention, and a power source 40.

In this embodiment, the guide wire 22 includes an elongated conductor 24having a longitudinal dimension with a proximal end 26 and a distal end28. The guide wire 22 further includes an insulator 30 overlying theelongated conductor. The insulator exposes a portion 32 of thelongitudinal dimension of the elongated conductor forming an electrodethat terminates with an electrode tip 34 at the distal end 28 of theguide wire 22. The elongated conductor 24 is arranged to be connected tothe power source 40 arranged to provide high voltage pulses to causeelectrical arcs at the electrode tip 34 that in turn form steam bubblesand shock waves to break the stenosis and/or open the occlusion 52 andpermit the guide wire 22 to pass there through.

The power source includes a high voltage pulse generator 42, a batterypower supply 44, a return pad or ground patch 46, which may have alarger surface area than the electrode tip of the guide wire, and anon/off control 48. The battery supply 44 lends to the portability andsafety of the system 20. The patch 46 is preferably the type that makesbroad surface contact with the patient's skin. The power source isconnected to the elongated conductor 24 of the guide wire 22 at ametallic ring 36. The ring 36, conductor 24, and power source lead 49are preferably connected together with solder or a crimp. An additionalreusable connector in lead 49 is not shown for simplicity.

The elongated conductor 24 and electrode tip 34 may be formed ofstainless steel, for example. The insulator 30 may be formed fromTeflon, for example, and arranged to cover the entire elongatedconductor 24 except at the distal end 34 to form the exposed electrodeportion 32. The electrode tip 34 is preferably generally spherical inshape. The pulse generator 42 is preferably arranged to provide voltagepulses of between about 300 and 3000 volts between the elongatedconductor 24 and the patch 46. The duration of the applied pulses ispreferably very short, on the order of 0.1 to 2.0 microseconds.

Without wishing to be bound by theory, a monopolar or unipolar electrodearrangement (such as described above) may give rise to a shock wave bygenerating a plasma arc across an electrolysis bubble. Such arc does notextend to a remote ground patch or return pad (in contrast to a bipolarelectrode arrangement, where the arc extends from the electrode to thereturn electrode). When a voltage is applied to the monopolar electrode,a low level of current may flow between the electrode and return pad,which may cause dissociation of hydrogen and oxygen in the surroundingfluid such that a gas bubble (e.g., an electrolysis bubble) forms at theelectrode tip 34. When the applied voltage is increased to a high value(e.g., from about 500 V to about 3000 V), a plasma arc forms at theelectrode tip and arcs across the gas bubble to the surrounding fluid.This plasma arc may generate sufficient heat to form a steam bubble inthe fluid, the formation of which gives rise to a first shock wave. Whenthe steam bubble collapses, a second shock wave may be formed. Incontrast to a bipolar system, the plasma arc does not extend from theelectrode tip to the return pad. Since the plasma arc generated by amonopolar system is shorter (e.g., the distance across a gas bubble)than that generated by a bipolar system (e.g., the distance between thefirst electrode and the return electrode), less heat is generated andtherefore, the magnitude of a shock wave generated by a monopolar systemmay be less than the magnitude of a shock wave generated by a bipolarsystem. The pulse magnitude, duration, frequency and/or duty cycle of amonopolar system may be adjusted to ensure that a shock wave ofsufficient force is generated to soften or crack the occlusion in theblood vessel.

In operation, the guide wire 22 is fed into the blood vessel 50 (e.g.,artery or vein) to place the electrode adjacent the occlusion 52. Thepatch 46 is adhered to the patient's skin to serve as a return path. Theon/off switch 48 is then turned on to permit the pulse generator 42 toprovide the high voltage pulses to the elongated conductor 24 and hencethe electrode portion 32 and electrode tip 34. Each pulse is ofsufficient amplitude and duration as mentioned above to cause a gas(steam) bubble to be formed at the electrode tip 34. Each gas bubble inturn causes a shock wave to form with each shock wave causing theopening in the occlusion to become enlarged. With each shock wave, theguide wire 22 may be advanced until the occlusion is crossed. The numberof shock waves required will depend upon the size and hardness of theocclusion. Typically, several pulses will be required. Various pulsetrains and waveforms may be used to generate one or more shock waves, asmay be desired to create an opening in a vascular occlusion. In somevariations, the duty cycle of the voltage waveform may be from about 1Hz to about 2 Hz, or from about 3 to about 5 Hz, e.g., 3 Hz. The pulsewidths may be less than or equal to about 3 μs, e.g., from about 0.1 μsto about 2 μs, from about 1 μs to about 2 μs, or less than 2 μs. Themagnitude of the voltage pulses may be from about 500 V to about 3000 V.A remote control (not shown) or foot switch or button 48 can be providedfor easy turn off by the physician. Both softer thrombus and calcifiedchronic total occlusions can be opened with the system of FIG. 1.

One variation of a method of using a shock wave guide wire in amonopolar configuration to create an opening in a vascular occlusion maycomprise the steps depicted in the flow diagram of FIG. 11A. Method 1100may comprise advancing a guide wire 1102 capable of generating one ormore shock waves (e.g., any of the guide wires described herein) withina blood vessel to a vascular occlusion (e.g., a chronic total occlusion)and advancing an angioplasty balloon catheter 1104 over the guide wireto the vascular occlusion. Optionally, a sheath or guide catheter may beintroduced into the vasculature, and the guide wire and/or angioplastyballoon catheter may be subsequently advanced through the sheath orguide catheter to access the vascular occlusion. The angioplasty ballooncatheter may or may not comprise a shock wave generator (e.g., one ormore shock wave electrodes) within the angioplasty balloon. Theangioplasty balloon may then be expanded 1106 before, after, orsimultaneously with visualizing 1108 the vascular occlusion. Thevascular occlusion may be visualized, for example, by using a dye thatis injected through a guide wire lumen of the angioplasty catheter.Alternatively or additionally, dye may be injected into the vasculaturevia a sheath or guide catheter through which the guide wire may beadvanced. Visualizing the occlusion may help a practitioner to confirmthat the shock wave guide wire is in contact with the occlusion.Expanding the angioplasty balloon may help a practitioner center theshock wave guide wire within the vessel lumen. Method 1100 may comprisegenerating one or more shock waves 1110 using the shock wave guide wireto create an opening in the occlusion (e.g., by activating a pulsegenerator as described above). Such opening may be confirmed byinjecting dye from the angioplasty catheter. Once it has been confirmedthat one or more openings has been created within the occlusion, theangioplasty balloon may optionally be deflated 1112 and the angioplastyballoon catheter may be advanced 1114 into the opening of the vascularocclusion. The angioplasty balloon catheter may then be used to performan angioplasty procedure 1116, with or without the generation ofadditional shock waves from the guide wire. The angioplasty ballooncatheter may soften or crack the calcifications remaining from theocclusion by generating shock waves within the angioplasty balloon(e.g., with shock wave electrodes located within the angioplastyballoon). Alternatively or additionally, the angioplasty ballooncatheter may soften or crack calcifications remaining from the occlusionby expanding the angioplasty balloon.

Another variation of a method of using a shock wave guide wire in amonopolar configuration to create an opening in an occlusion maycomprise the steps depicted in the flow diagram of FIG. 11B. Method 1120may comprise advancing a guide wire 1122 capable of generating one ormore shock waves (e.g., any of the guide wires described herein) withina blood vessel to a vascular occlusion (e.g., a chronic totalocclusion). Optionally, a sheath or guide catheter may be introducedinto the vasculature, and the guide wire may be subsequently advancedthrough the sheath or guide catheter to access the vascular occlusion.The method 1120 may comprise visualizing the occlusion 1124 after theguide wire has been advanced. For example, a dye may be delivered by acatheter (e.g., an angioplasty catheter where the balloon is notinflated) located upstream from the vascular occlusion and/or via asheath or guide catheter through which the guide wire may be advanced.Visualizing the occlusion may help a practitioner to confirm that theshock wave guide wire is in contact with the occlusion. Method 1120 maycomprise generating one or more shock waves 1126 using the shock waveguide wire to create an opening in the occlusion (e.g., by activating apulse generator as described above). Such opening may be confirmed byusing the same or different visualizing techniques of step 1124. Once ithas been confirmed that one or more openings has been created within theocclusion, method 1120 may comprise advancing an angioplasty ballooncatheter 1128 over the guide wire to the vascular occlusion. Theangioplasty balloon catheter may or may not comprise a shock wavegenerator (e.g., one or more shock wave electrodes) within theangioplasty balloon. The angioplasty balloon catheter may be advanced1130 into the opening of the vascular occlusion. The angioplasty ballooncatheter may then be used to perform an angioplasty procedure 1132, withor without the generation of additional shock waves from the guide wire.The angioplasty balloon catheter may soften or crack the calcificationsremaining from the occlusion by generating shock waves within theangioplasty balloon (e.g., with shock wave electrodes located within theangioplasty balloon). Alternatively or additionally, the angioplastyballoon catheter may soften or crack calcifications remaining from theocclusion by expanding the angioplasty balloon.

FIG. 2 is a perspective view, with portions cut away, showing furtherdetails of the shock wave guide wire system 20 of FIG. 1 in use with anangioplasty catheter. Here it may be appreciated that the shock waveguide system 20 may be employed to cross the occlusion 52 sufficientlyto enable an angioplasty catheter of the type well known in the art tobe carried on the guide wire 22 to a position within the occlusionopened by the shock wave guide wire system 20. To that end, theangioplasty balloon catheter includes Luer connectors 74, 76, and 78 atits proximal end 72, an angioplasty balloon 80, and a guide wire lumen82. The guide wire 22 is introduced onto the catheter 70 through theLuer connector 76 and into the guide wire lumen 82 until it extendsthrough the angioplasty balloon 80 and out the guide wire lumen 82. Oncethe shock wave guide wire system 20 opens the occlusion sufficiently,the balloon catheter 70 may be advanced down the guide wire to place theballoon 80 within the opening of the occlusion formed by the shock waveguide wire system to further open the occlusion 52 as necessary. FIG. 2also shows in the alternative negative polarity to the connection 22 andpositive to the skin electrode 46.

FIG. 3 is a perspective view, with portions cut away, showing stillfurther details of the shock wave guide wire system 20 of FIG. 1 in usewith the angioplasty catheter 70. Here it may be seen that the Luerconnector 76 may include two branches 77 and 79. The branch 77 acceptsthe guide wire 22. It includes a Tuey-Borst connector 81 that, whenturned, clamps down on the guide wire 22. This can be used as an anchorto longitudinally fix the guide wire. However, by loosening theTuey-Borst connector 81, the insulator 30 and conductor 24 (FIG. 1) ofthe guide wire 22 may be advanced and even rotated to obtain the mostadvantageous positioning of the guide wire 22. The other branch 79 ofthe Luer connector 76 may be attached to a source of saline 90, forexample. The saline may be employed to inflate the angioplasty balloon80 in a manner known in the art to further open the occlusion when it isin its proper position.

FIG. 4 is a perspective view of the guide wire of the shock wave guidewire system of FIG. 1 illustrating further aspects of the invention.FIG. 5 is a perspective view to an enlarged scale of the distal end ofthe shock wave guide wire illustrating further aspects of the inventionand FIG. 6 is a perspective view, to an exploded scale, illustratingparticular aspects of the distal tip electrode of the shock wave guidewire of FIG. 4. As may be seen in FIG. 4, the guide wire includes theTuehy-Borst connector 81 to anchor the insulator 30 and the elongatedconductor 24. The electrode portion 32 of the guide wire 22 that doesnot include insulation may be milled to a finer diameter and thenconfigured in a coiled configuration 33. This lends flexibility to thedistal end 28 of the guide wire 22. The coiled configuration 33 is thenterminated with the generally spherical electrode tip 34.

FIG. 5 shows an alternative manner of forming the coiled configurationin the electrode portion 32 of the guide wire 22. Here it may be seenthat the elongated conductor 24 is tapered at its end and receives aseparate coil 25 that is force fitted onto the taper of the conductor24. The coil may include a thin layer of insulation, such Teflon. Theelectrode tip 34 may then be force fitted onto the distal end of thecoil 25.

FIG. 6 shows structural details which the electrode tip may include. Theelectrode tip 34 may include a generally spherical portion 35 having anextension 37. The extension may be received within the coil 25. Theconductor 24, the coil 25, and the electrode tip 34 may all be formed ofstainless steel. Alternatively, the coil 25 may be formed of Tefloncoated platinum and the electrode tip 34 may be formed of tungsten orother similar material. The elongated conductor may have a diameter ofabout 0.013 inch and the insulation may be formed of Teflon, for exampleand have a thickness of about 0.0005 inch. The guide wire may thus havean overall diameter of about 0.014 inch which is one common size for aguide wire. Also, the electrode tip may have a diameter of 0.008 to0.014 inch. Still further, the electrode tip 34, instead of being ballshaped, may be formed of a single coil loop.

While heating of the blood and adjacent tissue may be controlled byadjusting the energy delivery of the high voltage pulses as describedsubsequently, active cooling of the therapy site is also an option. Asshown in FIG. 3, saline may be introduced in the angioplasty balloon 80to inflate it. That fluid could also be utilized for cooling purposes.Also, contrast could be added to the saline to provide visualization ofthe procedure. A 50/50 mix of saline and contrast would serve well. Thecooling may be injected down the guide wire lumen and withdrawn as welland replenished in a cooling cycle using Luer connection 78. Advancingand withdrawing a saline solution has the added advantage of debrisremoval. Loose debris from the chronic total occlusion can be withdrawnwith the fluid. Also, metal particles resulting from the arc therapy maybe removed as well.

FIG. 7 is a graph illustrating a manner in which a shock wave guide wiresystem embodying the invention may be operated according to anembodiment of the invention. As fully described in co-pendingapplication Publ. No. 2014/0074113 filed on Sep. 13, 2012 for BALLOONSHOCKWAVE CATHETER SYSTEM WITH ENERGY CONTROL, which application isowned by the assignee of the present invention and incorporated hereinby reference in its entirety, it has been found that effective shockwave intensity may be accomplished without holding the high voltagepulses on during the entire extent of their corresponding steam bubbles.Moreover, terminating the application of the high voltage before steambubble collapse can serve to preserve electrode material, permitting anelectrode to last for an increased number of applied high voltagepulses. Also, early termination of the high voltage can also be used toadvantage in controlling the temperature within the balloon fluid.

FIG. 7 is a graph illustrating a high voltage pulse applied to anelectrical arc shock wave producing electrode and the resulting currentflow through the electrode and it ground return in accordance with anembodiment of the invention. When the high voltage is first turned on,the voltage quickly rises to a level 100. During this time, as shown bydashed lines 102, the current is relatively low. After a dwell time(Td), the arc occurs at the electrode. At this time the steam bubblebegins to form and a high current begins to flow. In accordance withembodiments of the invention, responsive to the current flow, theapplication of the high voltage is terminated. This conserves energyapplied to the electrode, causing the electrode to remain useful for agreater number of pulses than otherwise would be the case if the highvoltage were applied longer or sustained throughout the bubbleexistence. The temperature of the blood and adjacent tissue is also heldto a lower than expected level because of the short duration of theapplied energy. The advantages of controlling the applied energy in thismanner are obtained without adversely affecting the intensity of theleading edge shock waves produced.

FIG. 8 is a schematic diagram of a power source for use in a shock waveguide wire system according to an embodiment of the invention and whichprovides the operation shown in FIG. 7. The power source 110 has anoutput terminal 112 that may be coupled to the elongated conductor 24 ofFIG. 1 and an output terminal 114 that may be coupled to the patchelectrode 46 of FIG. 1. A switch circuit 116 selectively applies a highvoltage on line 118 to the elongated conductor 24. A microprocessor 120,or other similar control circuitry, such as a gate array, controls theoverall operation of the source 110. A Field Programmable Gate Array(FPGA) may also be substituted for the microprocessor in a manner knownin the art. The microprocessor 120 is coupled to the switch 116 by anoptical driver 122. The switch includes a current sensor 124 thatincludes a current sensing resistor 126 that generates a signal that isapplied to an optical isolator 128 when the current flow reaches apredetermined limit, such as, for example, fifty (50) amperes.

In operation, the microprocessor 120 through the optical driver 122,causes the switch 116 to apply the high voltage to the elongatedconductor 24, and thus the electrode tip 34 (FIG. 1). The current sensedthrough resister 126 is monitored by the microprocessor 120 through theoptical isolator 128. When the current flow reaches a predeterminedlimit, as for example 50 amperes, the microprocessor 120 causes theapplication of the high voltage to be terminated. The forgoing occursfor each high voltage pulse applied to the elongated conductor 24 andthus the electrode tip 34. Each pulse creates a shock wave of consistentand useful intensity. Further, because the application of the highvoltage is terminated early, the electrode material is preserved tolengthen the useful life of the electrodes and the heat generated ismaintained at a low level.

FIG. 9 is a schematic diagram of another power source 130 for use in ana shock wave guide wire system according to another embodiment of theinvention. As will be seen, the power source 130 delivers a first lowvoltage across the elongated conductor 24 and the patch electrode 46(FIG. 1) to pre-grow the bubble at the electrode tip 34 and thereafterdelivers a second higher voltage to rapidly expand the pre-grown bubbleto cause the arc and the shock wave in a time controlled manner.

The source 130 includes control logic 140, a first transistor 142, asecond transistor 144, and output terminals 146 and 148. Output terminal146 is arranged to coupled the elongated conductor 24 (FIG. 1) andoutput 148 is arranged to be coupled to the patch electrode 46. Theoutput terminal 146 is connected to a 3,000 volt source.

Initially, the control logic 140 delivers a two millisecond (2 ms)control pulse 150 to the gate of transistor 142. This causes a low (forexample, 25 ma) current through the elongated conductor 24 and the patchelectrode 46 and a resistor 143. The low current applied for 2 ms formsa bubble on electrode tip 34 of a predictable size. After the 2 ms, thecontrol logic 140 turns transistor 144 on hard for 500 nanoseconds (500ns). This applies the full 3,000 volts to the elongated conductor. Thecontrol logic 140 may turn transistor 144 on hard immediately after the2 ms period or a short time thereafter, as for example, 10 microsecondsafter the 2 ms period. An arc and shock wave will occur essentiallyimmediately. Since the high voltage is applied for only a short time,here 500 ns, a reduced amount of energy is delivered. As a result, muchless heat is generated.

FIG. 10 is a graph illustrating another manner in which a shock waveguide wire system embodying the invention may be operated according toan embodiment of the invention with the power circuit of FIG. 9. First,a low voltage 190 is applied across the elongated conductor 24 and thepatch electrode 46 when transistor 142 is turned on for 2 ms. The lowvoltage assures that an arc will not occur. However, the low voltagedoes produce a low current 192 (25 ma) to flow. During this 2 ms period,a bubble of predictable size is grown on electrode tip 34. The bubblesize may be controlled by the amount of current and the length of timethe low current is applied. After the 2 ms period, the transistor 144 isturned on hard to apply a narrow pulse (500 ns) of the full 3,000 volthigh voltage 194. During this short time, a current of 250 amperes mayflow. The high voltage and current rapidly expands the pre-grown bubbleand within a short delay time DT causes the arc and shock wave to beproduced at 196. The arc and shock wave are produced quickly because thebubble had already been pre-grown by the low voltage 90. The voltage andcurrent fall quickly to zero at 198. For a more detailed discussionregarding the foregoing, reference may be had to co-pending applicationPubl. No. 2014/0052145 filed on Feb. 26, 2013 for SHOCK WAVE CATHETERSYSTEM WITH ARC PRECONDITIONING, which application is owned by theassignee of the present invention and incorporated herein by referencein its entirety.

As may be seen from the foregoing, the high voltage pulse is applied fora much shorter period of time to produce the arc and shock wave becausethe bubble had already been pre-grown by the preceding low voltage andcurrent. The overall arc energy is lower and the steam bubble will besmaller. This results in less energy being applied and therefore lessheat being generated.

While particular embodiments of the present invention have been shownand described, modifications may be made, and it is therefore intendedto cover in the appended claims all such changes and modifications whichfall within the true spirit and scope of the invention.

What is claimed:
 1. A guide wire system, for use in guiding an elongatedcatheter through an artery or vein of a mammalian body having a stenosisand/or an occlusion therein, the guide wire system comprising: a guidewire including an elongated conductor having a longitudinal dimension, aproximal end and a distal end and an insulator overlying the elongatedconductor, the insulator exposing a portion of the longitudinaldimension of the elongated conductor to form a monopolar electrode; anda source of high voltage pulses connected to the conductor, each pulsebeing greater than 300 volts and between 0.1 to 2.0 microseconds induration and delivered at a repetition rate between about 1 Hz and about5 Hz, each pulse creating an electrical arc at the electrode that inturn forms a steam bubble and a shock wave to break the stenosis and/oropen the occlusion.
 2. The system of claim 1, wherein the source of highvoltage is arranged to provide the elongated conductor with a highelectrical voltage at a comparatively low initial current through theelongated conductor and to terminate the high electrical voltage inresponse to a comparatively high current through the elongatedconductor.
 3. The system of claim 1, wherein the source of high voltageis arranged to deliver a first electrical voltage to the electrode thatgrows a bubble at the electrode and then thereafter to deliver a secondelectrical voltage to the electrode to create an arc at the electrodeand to rapidly expand the bubble to form a shock wave.
 4. The system ofclaim 1, wherein the elongated conductor of the guide wire has a distaltip end at the distal end of the elongated conductor and wherein themonopolar electrode is at the distal tip end of the elongated conductor.5. The system of claim 4, wherein the distal tip end of the elongatedconductor is generally spherical in configuration.
 6. The system ofclaim 5, wherein the distal tip end is formed of stainless steel.
 7. Thesystem of claim 4, wherein the insulator is formed of Teflon.
 8. Thesystem of claim 4, wherein the elongated conductor and insulator of theguide wire form a flexible coiled structure at the distal end of theelongated conductor.
 9. The system of claim 8, wherein the distal tipend of the elongated conductor is generally spherical in configuration.10. The system of claim 4, further including an anchor, the anchor beingreleasable to permit the elongated conductor and insulator to be movedlongitudinally and rotated.
 11. The system wire of claim 1 wherein eachpulse is less than 3,000 volts.
 12. A guide wire system, for use inguiding an elongated catheter through an artery or vein of a mammalianbody having a stenosis and/or an occlusion therein, the guide wiresystem comprising: a guide wire including an elongated member having alongitudinal dimension, a proximal end and a distal end, the guide wirecarrying a distal monopolar electrode at its distal end; a surfaceelectrode adapted to make broad surface contact with the skin of themammalian body; and a source of high voltage pulses coupled to thedistal electrode and to the surface electrode, each pulse being greaterthan 300 volts and between 0.1 to 2.0 microseconds in duration anddelivered at a repetition rate between about 1 Hz and about 5 Hz, eachpulse creating an electrical arc at the distal electrode that in turnforms a steam bubble and a shock wave to break the stenosis and/or openthe occlusion.
 13. The system of claim 12 wherein each pulse is lessthan 3,000 volts.
 14. The system of claim 12, wherein the source of highvoltage is arranged to provide the electrode with a high electricalvoltage at a comparatively low initial current and to terminate the highelectrical voltage in response to a comparatively high current throughthe electrode.
 15. The system of claim 12, wherein the source of highvoltage is arranged to deliver a first electrical voltage to theelectrode that grows a bubble at the electrode and then thereafter todeliver a second electrical voltage to the electrode to create an arc atthe electrode and to rapidly expand the bubble to form a shock wave. 16.The system of claim 15, wherein the distal end of the elongated memberis formed of stainless steel.
 17. The system of claim 12, wherein thedistal end of the elongated member is generally spherical inconfiguration.